David Smart
Simple demo for the Raio RA8875 Based Display with a 4-wire SPI interface.
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RA8875 Based Display Controller¶
This page shows a simple demo program for a graphics library supporting a low cost display from buydisplay.com. While the module can be configured for support via I2C, 3-Wire SPI, 4-Wire SPI, 8-bit Parallel or 16-bit Parallel, the companion library only supports the 4-Wire SPI.
Library¶
Display Pictures¶
The image captured by the camera has washed out the colors substantially.
With careful study of the image below, you can see a number of solder-blob jumpers. These jumpers are described quite well in the manual, and configure the many different options. The specific unit shown here is the "entry point" model, it does not have touchscreen, SD card, extra Font memory, or the key pad interface. As you see in the top left, it is wired with an 8-signal ribbon cable (but note in the schematic that it only needs 6 as the two power and two ground are internally connected together in the module).
Also note, that some configuration changes go beyond the jumpers. I decided to switch my configuration to 4-Wire SPI and had to remove R1, R2, and R3 (as well as changing some of the solder-blob jumpers). Had I ordered the display with the support for 4-Wire SPI, that would not have been necessary.
Schematic¶
The library should be able to work with any SPI port, and the Chip Select pin is a simple DigitalOut pin, chosen from the unused pins on my baseboard.
Sample Program¶
#include "mbed.h"
#include "RA8875.h"
Serial pc(USBTX, USBRX);
int main()
{
pc.baud(460800); // I like a snappy terminal, so crank it up!
pc.printf("\r\nRA8875 Test - Build " __DATE__ " " __TIME__ "\r\n");
RA8875 lcd(p5, p6, p7, p12, NC, "tft"); // MOSI, MISO, SCK, /ChipSelect, /reset, name
lcd.puts(0,0,
"RA8875 lcd(p5, p6, p7, p12, NC, \"tft\");\r\n\r\n"
"lcd.circle( 400,25, 25, BrightRed);\r\n"
"lcd.fillcircle( 400,25, 15, RGB(128,255,128));\r\n"
"lcd.ellipse( 440,75, 35,20, BrightBlue);\r\n"
"lcd.fillellipse( 440,75, 25,10, Blue);\r\n"
"lcd.triangle( 440,100, 475,110, 450,125, Magenta);\r\n"
"lcd.filltriangle( 445,105, 467,111, 452,120, Cyan);\r\n"
"lcd.rect( 400,130, 475,155, Brown);\r\n"
"lcd.fillrect( 405,135, 470,150, Pink);\r\n"
"lcd.roundrect( 410,160, 475,190, 10,8, Yellow);\r\n"
"lcd.fillroundrect(415,165, 470,185, 5,3, Orange);\r\n"
"lcd.line( 430,200, 460,230, RGB(0,255,0));\r\n"
"for (i=0; i<=30; i+=5)\r\n"
" lcd.pixel(435+i,200+i, White);");
lcd.circle( 400,25, 25, BrightRed);
lcd.fillcircle( 400,25, 15, RGB(128,255,128));
lcd.ellipse( 440,75, 35,20, BrightBlue);
lcd.fillellipse( 440,75, 25,10, Blue);
lcd.triangle( 440,100, 475,110, 450,125, Magenta);
lcd.filltriangle( 445,105, 467,111, 452,120, Cyan);
lcd.rect( 400,130, 475,155, Brown);
lcd.fillrect( 405,135, 470,150, Pink);
lcd.roundrect( 410,160, 475,190, 10,8, Yellow);
lcd.fillroundrect(415,165, 470,185, 5,3, Orange);
lcd.line( 430,200, 460,230, RGB(0,255,0));
for (i=0; i<=30; i+=5)
lcd.pixel(435+i,200+i, White);
while (1)
;
}